The present invention relates to thresholds such as are used in a doorway communicating from interior space to the outside and more particularly to a thermoplastic door threshold of unique configuration manufactured by blow molding techniques.
Thresholds, such as are associated with door assemblies, provide a transition from one space to another through a doorway (e.g. between flooring of different material and/or height) and can provide a sealing/weatherproofing barrier when the doorway provides communication between the outside and interior space. Traditionally, such "exterior" thresholds ("exterior" used in the sense of a doorway communicating to the outside environment) have been manufactured from wood, optionally clad with metal, such as aluminum. Such wooden thresholds were anchored to the lower, horizontal jamb of the door frame by means of screws. Weather-tightness can be a problem for such threshold assemblies due to weathering of the wood and the difficulty in adjusting the sill height to mate tightly against the bottom of the door.
Of more recent vintage are thresholds manufactured from thermoplastic material by conventional injection molding techniques (structural foam generation) and by extrusion techniques. Such thermoplastic thresholds provide excellent weatherability, provided that temperatures do not reach high or low extremes. Adjustable wooden sills can be accommodated by thermoplastic thresholds which is an advantage offered by using thermoplastic material. Additionally, weep systems can be provided. A weep system comprises means for channeling water that might accumulate in a channel designed to house the adjustable sill to the outside of the threshold. In this regard, U.S. Pat. Nos. 2,846,736, 3,261,130, and 3,900,967 show injection molded thermoplastic thresholds for doors. In particular, the '967 patent shows the general threshold shape and a weep system. The '130 patent shows the molding feature of threshold end pieces so screws can anchor the threshold sides to the door frame. U.S. Pat. Nos. 2,696,028, 3,778,931, and 4,104,830 show adjustable seal inserts and end wall construction of thermoplastic door thresholds. Finally, U.S. Pat. Nos. 3,360,887, 3,851,420, and 3,859,754 refer to extruded thermoplastic door thresholds.